JP2001175090A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent such the troubles that the abutting edge part of a cleaning blade abutting on the area of an intermediate transfer body is turned up and damaged, even in the case an image forming operation (especially, secondary transfer) is executed in a state where an area without the recording paper is increased in the intermediate transfer body, as for an intermediate transfer system image forming device. SOLUTION: The device is provided with a control means for executing a control of forming a toner band (belt-like toner image) TB crossing a specified area G in the specified area G which does not face the recording paper P among the transferable area M of the intermediate transfer belt 20 and also which is positioned outside the side end part of the recording paper P in the supplying direction S in the case the width Ws of the recording paper P in the supply direction S is narrower than a prescribed judgment reference value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer which employs an intermediate transfer system in which a toner image formed by an image forming apparatus is primarily transferred onto an intermediate transfer member and then secondary transferred onto a recording medium. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that is effective for solving a problem associated with a cleaning blade of a cleaning device that cleans a transfer surface of an intermediate transfer member by contacting the surface.

[0002]

2. Description of the Related Art In recent years, as an image forming apparatus such as a color printer or a color copying machine using an electrophotographic system or the like, a type employing an intermediate transfer system is increasing. A color image forming apparatus employing such an intermediate transfer system is shown in FIG.
As illustrated in a, one or a plurality of image forming apparatuses 100 form a toner image for one color or a plurality of colors on an image carrier 110 including a drum-shaped or belt-shaped photoconductor by an electrophotographic process, The respective toner images are primarily transferred so as to be superimposed on a belt-shaped or drum-shaped intermediate transfer member 200 that rotates (rotates) so as to pass through the transfer portion N1 of the image carrier 110, and then the intermediate transfer member 200 Is transferred to a recording medium P, such as plain paper, cardboard, or OHP sheet, which is supplied so as to pass through the transfer portion N2 of the intermediate transfer body, so that a desired color is obtained. An image or the like is formed. In addition, the intermediate transfer body 200 after the secondary transfer is usually attached to the transfer surface by a cleaning blade 270 of a cleaning device arranged so as to contact the transfer surface on which the toner image is transferred. The toner and the like are scraped off and cleaned.

[0005] Reference numeral 150 in FIG. 8 denotes a roll for electrostatically transferring the toner image on the image carrier 110 from the image carrier to the intermediate transfer member 200 by a transfer electric field formed by applying a primary transfer bias. A primary transfer device (specifically, a primary transfer roll), 210, 220, and 230 are support rolls around which an intermediate transfer member (belt) 200 is wound;
Is a roll type secondary transfer device (specifically, a roll type secondary transfer device that electrostatically transfers a toner image on the intermediate transfer member 200 from the intermediate transfer member to the recording medium P by a transfer electric field formed by applying a secondary transfer bias. Is a secondary transfer roll).

[0004]

However, in an image forming apparatus employing such an intermediate transfer system, FIG.
As shown in FIG. 8B, the recording medium P having a relatively narrow width Ws in the supply direction S (FIG. 8A) is the intermediate transfer body 2.
00 and a secondary transfer unit (secondary transfer roll) 250, which is supplied to a secondary transfer unit where the recording medium P does not exist (in other words, the intermediate transfer body 200 and the secondary transfer unit 200). When the area (E) where the next transfer roll 250 directly contacts is widened, the area E of the intermediate transfer body 200 where the recording medium P does not exist is the cleaning blade 2 of the cleaning device.
After passing through the intermediate transfer member 70, as shown in FIG.
Troubles such as turning over or damage of Oa occur. FIG. 9a shows the state of the normal contact edge.

[0005] The trouble related to the cleaning blade is that a discharge product generated by the application of the secondary transfer bias adheres to the area E of the intermediate transfer member 200 where the recording medium P does not exist, or the area E Are damaged by a transfer current flowing between the secondary transfer device 250 and the secondary transfer device 250 in accordance with the application of the secondary transfer bias.
It is recognized that this is caused by the fact that the frictional force (friction coefficient) with the cleaning blade in the region E increases as compared with the other regions.

For this reason, the secondary transfer device adjusts the voltage of the secondary transfer bias according to environmental conditions (temperature and humidity), the type of recording medium P (for example, cardboard, OHP (Over Head Projector) sheet, label paper, etc.). When the secondary transfer bias is set to a higher voltage value, the adhesion of the discharge products and the damage due to the transfer current tend to further increase when the secondary transfer bias is set to a higher voltage value. Therefore, the frictional force in the region E of the intermediate transfer member 200 where the recording medium does not exist further increases, and as a result, troubles related to the cleaning blade are likely to occur. Therefore, for example, when a “postcard” having a particularly small width and made of thick paper is supplied as the recording medium P, the area E where the recording medium (postcard) of the intermediate transfer body does not exist in the secondary transfer unit is present. In addition to the condition that the secondary transfer bias increases, the condition that the secondary transfer bias at that time is set to be higher than that of the plain paper overlaps, so that it becomes more remarkable.

If a trouble relating to such a cleaning blade occurs, the intermediate transfer member 20
At least a partial area E of the cleaning blade 27
Since the cleaning is not performed normally due to 0, if an image is formed (secondarily transferred) in the area E where the cleaning has failed, there is a problem that the image quality is adversely affected.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to properly solve a problem such as turning or damage of a contact edge portion of a cleaning blade which contacts an intermediate transfer member. It is an object of the present invention to provide an intermediate transfer type image forming apparatus which can perform the above-described operations.

[0009]

According to the present invention, an image forming apparatus for forming a toner image on an image carrier in accordance with image information, and an image carrier for the image forming apparatus. An intermediate transfer member that circulates so as to pass through a transfer section of the body and transfers a toner image formed on the image carrier, and a primary transfer device that primarily transfers a toner image from the image carrier to the intermediate transfer member And a secondary transfer by a transfer electric field formed by applying a secondary transfer bias to a recording medium supplied so that the toner image primarily transferred to the intermediate transfer body passes through a transfer portion of the intermediate transfer body. A secondary transfer device for cleaning, a cleaning device for cleaning a transfer surface of the intermediate transfer body on which the toner image is transferred by a cleaning blade abutting on the transfer surface, and a width or a width and a length in the supply direction of the recording medium Acknowledge The width of the recording medium in the supply direction is smaller than a predetermined reference width, at least an area of the transferable area of the intermediate transfer body that does not face the recording medium. And a control means for executing control for forming a toner image in a specific area outside the side end in the supply direction of the recording medium.

Here, the predetermined judgment reference width is not particularly limited, but is based on a width at which it is estimated that troubles such as curling or damage of the contact edge of the cleaning blade are likely to occur. Is set to Further, the recognition means only needs to have a function capable of recognizing at least the width or information on the width and length of the recording medium to be used for image formation to be performed. The toner image formed in the specific area usually has a linearly continuous band shape crossing the specific area of the intermediate transfer body (in a direction orthogonal to the direction in which the intermediate transfer body rotates). Is preferable, but there are no particular restrictions on the conditions relating to the form and the like, as long as troubles relating to the cleaning blade can be reliably prevented with as little toner as possible.

According to the image forming apparatus of the present invention, when the width of the recording medium in the supply direction is narrower than the predetermined reference width, at least an area of the transferable area of the intermediate transfer body that does not face the recording medium. Then, a toner image is formed in a specific area outside the side end of the recording medium in the supply direction. As a result, the toner is supplied by the toner image formed at least in the area where the frictional force is most likely to increase in the area where the recording medium of the intermediate transfer body does not exist at the time of the secondary transfer, and the toner is present. Functions as a lubricant between the contact edge portion of the cleaning blade and the intermediate transfer member. As a result,
When an area of the intermediate transfer member where the recording medium does not exist arrives at the cleaning blade, at least the toner image is supplied to the cleaning blade and functions as a lubricant. The frictional resistance between the blade and the abutting edge of the cleaning blade is significantly reduced, so that the abutting edge of the blade is hardly turned or damaged.

When the secondary transfer device is configured to variably set the voltage of the secondary transfer bias, the control means in the present invention sets the voltage of the secondary transfer bias to be lower than a predetermined judgment reference voltage. It may be configured to execute a control for forming a toner image in the specific area when the setting is high. The predetermined judgment reference voltage is not particularly limited, but is set based on a voltage value when it is estimated that a trouble relating to the cleaning blade as described above is likely to occur.

With this configuration, when the width of the recording medium in the supply direction is narrow and the secondary transfer bias is set to a higher voltage under a predetermined condition, the above-mentioned intermediate transfer member can be identified. A toner image is formed in the area. Thereby, in the area where the recording medium of the intermediate transfer body does not exist,
In a region where the frictional force is likely to increase due to the application of a high secondary transfer bias, the toner image reliably supplies toner to the region.

[0014] The control means in the present invention is configured such that the secondary transfer device variably sets a voltage of a secondary transfer bias according to the type of the recording medium, and the recognizing means includes a recording medium. When the recording medium is a thick paper, an OHP sheet or a label paper, the control for forming the toner image in the specific area may be executed.

With this configuration, the width of the recording medium in the supply direction is narrow, and the recording medium is thick paper, OH.
When a P sheet or label paper is used, a toner image is formed in a specific area of the above-described intermediate transfer body. As a result, in the three types of recording media described above, the transferability generally tends to decrease, so that the secondary transfer bias is set to a high voltage value. Even in an area where the frictional force is likely to increase due to the application of such a high secondary transfer bias, the toner is reliably supplied and present by forming the toner image.

Further, the control means according to the present invention, when the length of the recording medium in the supply direction is shorter than a predetermined judgment reference length, transfers the toner image in the specific area to the specific area of the intermediate transfer member. In this case, it is preferable to execute control to be formed in a region from the rear end of the recording medium in the supply direction to the upstream side in the circumferential movement direction of the intermediate transfer body. The predetermined judgment reference length is not particularly limited, but is set based on the length when it is estimated that the trouble relating to the cleaning blade described above is likely to occur.

In such a configuration, when the length of the recording medium in the supply direction is shorter than the predetermined determination reference length, the toner image is formed on the intermediate transfer member more than the rear end of the recording medium in the supply direction. It is formed in a specific area on the rear side.
As a result, the toner image in the specific area does not exist in the area of the intermediate transfer body when the recording medium passes through the secondary transfer section and the secondary transfer is performed. Is not transferred to the secondary transfer device side.

The control means according to the present invention may be arranged such that the secondary transfer device is configured to apply a secondary transfer bias only while the secondary transfer is being performed and not to apply the bias at other times. It is preferable that control is performed so that a toner image in a specific area is formed in a specific area of the intermediate transfer member, to which no secondary transfer bias is applied.

In such a configuration, the toner image is formed in a specific area of the intermediate transfer member, in which no secondary transfer bias is applied. As a result, the toner image does not exist in the area of the intermediate transfer body when the secondary transfer is performed by applying the secondary transfer bias, and the toner image is transferred to the secondary transfer device side. It will not be done.

Further, the control means in the present invention includes:
The secondary transfer device includes a detachable pressing member that presses the recording medium against the intermediate transfer member at the time of the secondary transfer, and causes the pressing member to contact the intermediate transfer member only while the secondary transfer is performed. In the case where the toner image is configured to be separated from the intermediate transfer body at the time of the control, the toner image in the specific area should be formed in the specific area of the intermediate transfer body and the area where the pressing body is separated. May be configured to be executed.

In such a case, the toner image is formed in a specific area of the intermediate transfer member, and the pressing member of the secondary transfer device is separated from the intermediate transfer member. As a result, the toner image does not exist in the area of the intermediate transfer body when the pressing body is in contact with the secondary transfer and the toner image is transferred to the secondary transfer device side. I won't.

Further, the control means according to the present invention, when the image forming apparatus is configured to form a plurality of toner images corresponding to the number of colors by using a plurality of toners having different colors, It is preferable to execute a control for forming a toner image in a specific area by sequentially using the plurality of color toners.

In the case of such a configuration, the toner image in the specific area is formed by using a plurality of toners sequentially.
As a result, the plurality of toners are consumed at substantially the same ratio, and there is no possibility that only a part of the toner is consumed and consumed for forming the toner image.

In the above-mentioned image forming apparatus of the present invention, when the cleaning device is configured to move the cleaning blade toward and away from the intermediate transfer member, the control means may include at least a cleaning blade of the cleaning device. When the toner image in the specific area arrives, it is preferable to execute a control to be brought into contact with the intermediate transfer member.

With this configuration, the toner image formed on at least the specific area of the intermediate transfer member is reliably supplied to the cleaning blade, and is reliably scraped off by the blade.

The image forming apparatus of the present invention has at least a drum-shaped or belt-shaped photosensitive member or an image carrier made of a dielectric material on which a toner image can be formed. Any of a plurality may be used. In the case of a color image forming apparatus, the toner images of each color constituting the color image may be sequentially formed by one image forming apparatus, or may be formed one by one by a plurality of image forming apparatuses. You may comprise. The intermediate transfer member has a belt-like shape or a drum-like shape.

[0027]

[First Embodiment] FIG. 2 is a schematic diagram showing an intermediate transfer type color printer according to an embodiment of the present invention. In the figure, reference numeral 10 denotes an image forming unit (image forming apparatus), 20 denotes an intermediate transfer belt (intermediate transfer body), and P denotes a recording sheet (recording medium).

The image forming unit 10 forms a toner image T on a photosensitive drum (image carrier) 11 according to image information transmitted from an externally connected device (such as a personal computer) connected to the printer. is there.

The image forming unit 10 in this embodiment
Is a roll-type charging device 12 that uniformly charges the surface of the photosensitive drum 11 around the photosensitive drum 11 that is driven to rotate in the direction of arrow A, and forms an electrostatic latent image on the surface of the photosensitive drum 11 by exposure. A laser beam type latent image forming device (for example, ROS: Raster Output Scanner) 13, a rotary type developing device 14 for developing the electrostatic latent image with a toner (developer) of a predetermined color to visualize, An image forming apparatus related to the electrophotographic process, such as a blade type drum cleaner 15 for removing and cleaning untransferred toner remaining on the surface of the drum 11, is provided. Of these, the rotary type developing device 14 includes developing devices 14Y, 14M, and 14 in which yellow (Y), magenta (M), cyan (C), and black (B) toners are stored one by one.
C and 14K are arranged at equal intervals along the peripheral surface of the rotary support 14a, and the rotary support 14a is rotated by a predetermined angle to thereby develop the toner containing the toner color corresponding to the color of the electrostatic latent image. The photosensitive drum 11 is positioned so as to be close to the developing position.

In the image forming unit 10, when a print start instruction is received, the surface of the photosensitive drum 11, which is driven to rotate at a predetermined speed in the direction of arrow A, is brought to a predetermined potential by a charging roll 12 of a charging device. The photosensitive drum 11 is uniformly charged, and then the ROS 13
The laser beam Bm modulated according to the image information is scanned and exposed to form an electrostatic latent image. Next, the electrostatic latent image is developed by the developing device 14 (Y, M, C, B) of the developing device 14 in which the toner corresponding to the color of the latent image is stored. As a result, a toner image T of a color corresponding to the electrostatic latent image is formed on the photosensitive drum 11. On the other hand, the surface of the photosensitive drum 11 after the transfer is cleaned by the drum cleaner 15.

The intermediate transfer belt 20 is connected to a transfer section (primary transfer section N) of the photosensitive drum 11 of the image forming unit 10.
The toner image T formed on the photosensitive drum 11 while being circulated so as to pass through 1) is transferred.

The intermediate transfer belt 20 in this embodiment
Consists of an endless belt made of synthetic resin film or rubber (conductive polyimide in this example), and a plurality of rolls 21 to
24 (for example, the drive roll 21, the tension roll 2
2. It is stretched around the backup roll 23 and the driven roll 24) and is driven to rotate at a predetermined speed in the direction of arrow B. Also, the photosensitive drum 11 of the intermediate transfer belt 20
A primary transfer bias roll 26 which constitutes a part of the primary transfer device 25 is disposed on the back side opposite to the first transfer device 25. Is applied with a primary bias having a polarity opposite to the charging polarity. Further, on the outer peripheral side (primary transfer portion N1) of the intermediate transfer belt 20 opposed to the driven roller 24, a belt cleaner 29 provided with a cleaning blade 28 that contacts and cleans the transfer surface on the front side of the belt 20. (Cleaning device) is provided. The belt cleaner 29 is rotated in a direction indicated by an arrow around a fulcrum 29 a by a solenoid (or a cam mechanism) (not shown), so that the cleaning blade 28 can be moved toward and away from the intermediate transfer belt 20. As the blade 28, a blade made of urethane rubber or the like is used, and the blade 28 is set so that the contact pressure is about 30 g / mm.

On the outer peripheral side (secondary transfer section N2) of the intermediate transfer belt 20 facing the backup roll 23, a secondary transfer roll (pressing member) 31 constituting a part of the secondary transfer device 30 is provided. It is arranged. Further, the secondary transfer device 30 is provided with a power supply roll 3 on the backup roll 23 side.
2, a secondary bias having the same polarity as the charged polarity of the toner on the intermediate transfer belt 20 is applied from the second bias power supply device 33. Further, the secondary transfer roll 31 is displaced in the direction of the arrow by a solenoid (or a cam mechanism) (not shown) so that the secondary transfer roll 31 can be moved toward and away from the intermediate transfer belt 20. In addition, the secondary transfer roll 31 includes:
A roll cleaner 34 having a cleaning blade 34a for contacting and cleaning the roll surface is provided.

Further, a paper tray (including a manual feed tray (not shown)) is provided at a secondary transfer portion (nip portion) N2 of the intermediate transfer belt 20 where the secondary transfer roll 31 contacts.
Recording paper P of a predetermined size and type stored in
Is supplied in accordance with the secondary transfer timing. In this embodiment, a predetermined recording paper P is sent out from a paper tray 35 by a feed roll 36, and then conveyed to a registration roll 38 via a paper conveyance path including a plurality of conveyance rolls 37 and the like. The sheet is fed into the secondary transfer portion N2 by the registration roll 38 in synchronization with the secondary transfer timing. A dashed line with an arrow in the drawing indicates a transport path of the recording paper P.

The toner image T previously formed on the photosensitive drum 11 is primarily transferred to the intermediate transfer belt 20 at a primary transfer portion (nip portion) N1 where the photosensitive drum 11 and the intermediate transfer belt 20 abut. The primary transfer is performed on the transfer surface of the intermediate transfer belt 20 by the transfer electric field formed by the primary transfer bias applied from the roll 26. Next, the toner image T transferred to the intermediate transfer belt 20 is transferred to the intermediate transfer belt 20 and the secondary transfer roll 3 with the rotation of the belt.
1 is conveyed to the secondary transfer contact (nip) portion N2 where the backup roll 2 contacts the backup roll 2 via the power supply roll 32.
3, the recording paper P supplied to the secondary transfer portion N2 by the transfer electric field formed by the secondary bias applied from
Is subjected to secondary transfer.

Here, when a single-color image is formed, the single-color toner image T primarily transferred onto the intermediate transfer belt 20 is formed.
Is immediately transferred to the recording sheet P, but when a color image is formed by superimposing toner images of a plurality of colors,
The steps of forming the respective toner images on the photosensitive drum 11 and the primary transfer of the toner images are repeated by the number of colors. For example, when forming a full-color image in which four color toner images are superimposed, yellow, magenta, cyan, and black toner images are sequentially formed on the photosensitive drum 11 and are primarily transferred to the intermediate transfer belt 20 in the order of formation. You. On the other hand, the intermediate transfer belt 20 holds the photosensitive drum 11 while holding the yellow toner image primarily transferred first.
The magenta, cyan, and black toner images are sequentially transferred at the primary transfer position such that the magenta, cyan, and black toner images are superimposed on the yellow toner image.

When a color image is formed, a plurality of toner images are multiplex-transferred so as to be superimposed on the intermediate transfer belt 20 as described above. Therefore, as described above, the belt cleaner 29 and the secondary transfer roll 31 are used. Contacts or separates from the intermediate transfer belt 20 at a predetermined timing. In this embodiment, basically, with respect to the belt cleaner 29, the leading end (top margin) of the maximum transferable area M of the intermediate transfer belt 20 passes through the contact position of the cleaning blade 28 with the intermediate transfer belt. The contact is made shortly before the contact is made, and is separated shortly after the rear end of the maximum area Q passes. Also,
As for the secondary transfer roll 31, the toner image (image area) that is primarily transferred to the intermediate transfer belt 20 is transferred to the secondary transfer portion N2.
Are set just before passing through, and are separated immediately after the rear end of the image area passes. further,
It is set so that the secondary transfer bias is applied to the backup roll 23 and stopped so as to be substantially linked to the timing of the contact / separation operation of the secondary transfer roll 30. Thus, at least the toner image first-transferred first to the intermediate transfer belt 20 is prevented from touching the cleaner 29 and the secondary transfer roll 20 and being disturbed. The surface of the intermediate transfer belt 20 after the secondary transfer is cleaned by a belt cleaner 29 (actually, a cleaning blade 28).

Finally, the recording paper P after the secondary transfer of the toner image T is sent to the fixing device 40 and subjected to fixing processing. The fixing device 40 is arranged so as to rotate in a state where the heating roll 41 and the pressing roll 42 are pressed against each other, and the recording paper is placed in a fixing nip portion which is a pressing portion between the two rolls 41 and 42. P is introduced and passed therethrough. Therefore, after the secondary transfer, the intermediate transfer belt 2
The recording paper P peeled from 0 is sent to the fixing nip portion of the fixing device 40 and passes therethrough, whereby the toner image is heated and pressurized and fixed on one side of the recording paper P. In addition,
As the pressure roll 42 in the fixing device 40, a pressure roll having a heating function may be used, or a belt type (belt nip type) instead of a roll type may be used. Then, the recording paper P after the completion of the fixing is discharged from the fixing device 40 and then discharged from the discharge roll 43.
The paper is conveyed and discharged outside the apparatus or to a post-processing device (or a double-sided conveyance path in the case of double-sided printing).

Through the above steps, the basic image forming process (single-sided printing operation) by this printer is completed.

By the way, in this color printer, it is possible to use a maximum of A3 size (18 × 13 inch) standard size paper as the recording paper P. In addition to plain paper, thick paper (for example, postcard), OHP sheet, It is configured to be able to use paper types such as label paper and envelopes. Further, when the various types of paper P are entirely rectangular, the paper P is fed vertically (LEF:
The paper image state shown in FIG. 2A) or the paper feeding (SEF: see the paper image state shown in FIG. 2B) with its short side vertically set is appropriately selected according to the image content to be printed. It is configured to be able to.

The secondary transfer device 30 is configured so that the voltage value of the secondary transfer bias can be variably set according to the type of the recording paper P. That is, the secondary transfer bias is, for example, “1.2 kV” for plain paper, “1.6 kV” for thick paper, “2.1 kV” for OHP sheet, and “1.5 kV” for label paper.
V "and" 1.3 kV "for envelopes.

Due to the adoption of such a configuration, for example, as shown in FIG. 3A, a recording paper P having a large size as a whole (for example, A3-size paper)
There is no particular problem in the case where is used or supplied (for example, A4 size paper is fed horizontally) in a state where the width Ws in the supply (feed) direction S is relatively wide. However, as illustrated in FIG. 3B, when a recording sheet Pn having a relatively narrow width Ws in the supply (feeding) direction S (for example, A4 size sheet (vertical feed), postcard, etc.) is used as the recording sheet P. As described above, in the secondary transfer section N2, the area where the narrow recording sheet Pn does not exist between the intermediate transfer belt 20 and the secondary transfer roll 31 (non-sheet passing section) E occurs. FIG. 3 schematically shows the state of the intermediate transfer belt 20 when the above-mentioned area E occurs. An area M surrounded by a dotted line in the figure is a toner area of the entire area (developed surface) of the intermediate transfer belt 20. Statue (image)
Is the maximum area in which the primary transfer can actually be performed (the maximum transferable area), and the area Pi surrounded by the solid line is the image area for the recording paper Pn.

The area E where the recording paper does not exist is
As described above, when the area E passes through the belt cleaner 29, the contact edge of the cleaning blade 28 may be turned up or damaged. It happens.

Therefore, in this color printer,
Means for forming a belt-shaped toner image (hereinafter, also referred to as “toner band”) TB in a specific area of the intermediate transfer belt 20 under a predetermined condition is adopted to prevent the occurrence of trouble relating to the cleaning blade.

FIG. 4 is a block diagram showing a control device (control means) for executing control for forming the toner band TB.

This control device includes an arithmetic processing unit (for example, CP
U) 60 are connected to a ROM 61 storing various control programs and the like and a RAM 62 storing various data to be read and written. Further, the arithmetic processing unit 60 recognizes the information of the width Ws and the length Ls with respect to the supply direction S of the recording paper P and the information of the paper type (when the printer itself has the recognition detecting function). Paper recognition unit (recognition means) 70, temperature / humidity sensor 71 for detecting temperature and humidity in the printer main body, external input / output unit 63 to which input data from an externally connected device and output data to the externally connected device are input An operation panel (user interface) operation setting 64 with a liquid crystal screen on which operation contents and condition settings of the printer are performed or operation contents and setting contents are displayed is connected.

Further, the arithmetic processing unit 60 includes various operations of the image forming unit 10 (rotation driving of the photosensitive drum 11, charging operation of the charging device 12, latent image forming operation of the latent image forming device 13, and operation of the developing device 14). Controller 65 for controlling the image forming unit, which controls the operation of the intermediate transfer belt 20, a controller 66 for the intermediate transfer belt, which controls each operation related to the intermediate transfer belt 20 (rotation driving of the belt, transfer operation of the primary transfer device 25, etc.)
The controller 67 for the secondary transfer device, which controls each operation of the secondary transfer device 30 (the operation of selecting and applying the voltage of the secondary transfer bias, the contact / separation operation of the secondary transfer roll 31), and the intermediate transfer of the belt cleaner 29. A contact / separation controller 68 that controls a contact / separation mechanism that performs a contact / separation operation with the belt 20 is connected.

In the ROM 61, for example, FIG.
As shown in FIG.
A predetermined control program for forming is stored. In this embodiment, whether or not the recording paper P is of the paper type to which the toner band is applied, whether or not the paper width Ws is equal to or smaller than the determination reference value (K), and whether the paper length Ls is the determination reference value (J) determine whether or not:
The RAM 62 stores data such as initial values and judgment reference values used in the toner band forming control program (particularly in a non-volatile memory portion). In this embodiment, as the above-mentioned paper type, “all types of paper are targeted”
Is set as “2” as the paper width determination reference value K.
17 mm ”is set to“ 3
77 mm "is stored as an initial value. The paper type and the determination reference values K and J can be changed.

Next, the control operation for the toner band will be described with reference to the flowchart shown in FIG.

First, upon receiving a print start command (step S101), the control device determines whether or not the recording paper P used for the print is of a type to which the toner band is applied (S102). In this printer, print conditions (paper type, paper size, paper feed direction, number of prints, etc.) are input from an external input / output unit 63 from an externally connected device. The initial setting of the paper type to which the toner band is applied is "all types" as described above. In the case of this initial setting, step S10
All of the judgments in 2 result in YES.

Next, the width W in the supply direction of the recording paper P
“s” becomes the criterion value K of the toner band application target “21”
6 mm or less ”(S103), and if it is less than 6 mm, the toner band application target sheet counter value N stored in the RAM 62 (initial value = 0).
Is added by "1" (S104). At this time, the paper width Ws
Is larger than 216 mm, the counter value N is not added. Here, description will be made on the assumption that plain paper is used as the recording paper P.

Subsequently, the target paper counter value N
Is greater than or equal to the accumulated print value (initial value = 1) of the toner band application target paper (narrow recording paper Pn), which is the threshold value for determining whether or not to execute the actual toner band forming operation. (S105) Then, the length Ls in the supply direction at that time is the reference value J of "377 mm
It is determined whether or not “less” (S106). In particular,
In these two steps S105 and S106, it is preferable that the toner band is formed on the recording paper Pn for which the result of the determination in step S104 is "YES". This is an additional judgment that is made for the purpose of suppressing the number of times.

Then, in this step S106, Y
If it is determined to be ES, the target recording paper P
The toner band forming operation is executed during the printing operation of n (S107). In this embodiment, the reference value of the band (line) width of the toner band TB is set to “2 mm”, and the formation position is set to “the recording paper Pn and the secondary transfer portion N2 in the transferable area M of the intermediate transfer belt 20”. In the specific region G (substantially equivalent to the non-sheet passing portion E) outside the side edge of the recording sheet Pn in the supply direction S of the recording sheet Pn. In addition, as for the formation position of the toner band TB, “in the transferable area MH on the upstream side in the rotation direction B of the intermediate transfer belt 20 from the rear end of the recording paper Pn” is set as the initial reference position. The reference value of the density gradation of the toner band TB is set to 50%.

As a result, as shown in FIG. 1, the recording paper Pn to be subjected to the toner band is placed on the intermediate transfer belt 20.
A toner band TB is formed together with the image PI. That is, the toner band TB in this embodiment is the same as the above-mentioned “specific area G (the area hatched to the right in FIG. 1) in the maximum transferable area M of the intermediate transfer belt 20.
And the area (the area where the oblique lines intersect) G.MH that satisfies the "inside the transferable area MH on the upstream side (the area with diagonal lines diagonally to the lower right in FIG. 1)". Moreover, the toner band TB has at least the area G
A continuous band is formed over the entire width of the MH (the length obtained by subtracting the width Ws of the recording paper from the width of the maximum transferable area M). A region indicated by a two-dot chain line in FIG. 1 is a boundary line indicating the width Ws and the length Ls of the largest recording sheet on which the toner band TB is to be formed in this embodiment (in other words, the determination reference value K , J).

By the formation of the toner band TB, when the area E (or G) of the intermediate transfer belt 20 where the recording sheet Pn does not exist passes through the belt cleaner 29 after the secondary transfer, the toner band TB is also supplied to the cleaning blade 28 of the belt cleaner 29. As a result, the toner in the toner band TB functions as a lubricant. As a result, the contact edge portion of the cleaning blade 28 is turned up or damaged due to the passage of the area (transfer surface) E of the intermediate transfer belt 20. No trouble occurs.

Therefore, according to this color printer, the above-mentioned area (transfer surface) E of the intermediate transfer belt 20 is not properly cleaned by the belt cleaner 29, which adversely affects the print quality thereafter. Also does not occur. Therefore, even when printing is performed on a recording sheet having a narrow width in the supply direction (strictly speaking, when printing is performed on a wide recording sheet immediately after the printing), a normal print without image quality deterioration due to poor cleaning is obtained. It becomes possible.

In this printer, the application of the secondary transfer bias is stopped and the areas G and MH where the toner bands TB are formed are stopped, as shown in FIG. Is the intermediate transfer belt 20
The toner band TB is not transferred to the secondary transfer roll 30 since the toner band TB is separated from the secondary transfer roll 30. As a result, in the subsequent secondary transfer, there is no possibility that the back surface of the recording paper (the surface in contact with the secondary transfer roll 31) is stained by the toner attached to the transfer roll side. Further, since the areas G and MH correspond to areas where no recording paper exists, the toner of the toner band TB is not transferred to the recording paper.

The toner band TB is supplied to the belt cleaner 29 after passing through the secondary transfer portion as described above, and is finally scraped off from the intermediate transfer belt 20 by the cleaning blade 28 to be removed. Is done. As a result, the toner band does not hinder subsequent printing.

FIG. 6 shows a state of a control operation relating to the toner band when printing is performed using a postcard as the recording paper P. The print at this time may be either a monochrome print or a color print.

That is, when printing two postcard print images (toner images) per rotation of the intermediate transfer belt 20 (so-called 2-up print), the initial setting values are as shown in FIG. As described above, the toner band TB is formed together with the two postcard print images every two up-prints. At this time, the toner band TB is formed in an area on the upstream side of the rotational movement of the belt from the rear end of the second postcard. Further, each toner band TB at this time is
Since it is formed in the separated area of the secondary transfer roll 30,
The belt cleaner 29 that is not transferred to the secondary transfer roll 30 and is in contact with the intermediate transfer belt 20
The cleaning blade 28 is supplied and removed.

When two-up printing is performed on such a small-sized postcard, the area E (G) of the intermediate transfer belt 20 where no recording paper (postcard) is present becomes large, and the voltage of the secondary transfer bias is increased. Since the value is higher than that of plain paper, the area of the intermediate transfer belt 20 where there is no postcard (particularly, the area where the secondary transfer is actually performed) is more susceptible to adhesion of electrostatic products and damage due to transfer current. You are in a harsh condition where the frictional force tends to increase most. However, in this printing, since the toner band TB is always formed in the area and supplied to the cleaning blade 28, the contact edge of the blade is not turned or damaged.

FIG. 7 shows a representative example of a control operation relating to a toner band when full-color printing is performed.

FIG. 9A shows the operation in the case where a single color image (toner image) of a narrow recording paper Pn is formed one by one (continuously or intermittently) in the maximum transferable area M of the intermediate transfer belt 20. For example, a toner band TB is formed using yellow (Y) toner during color printing for one sheet, and a magenta (M) color is formed during color printing for the next sheet. The toner of the four colors is sequentially used such that the toner band TB is formed by using the toner of the first color and the toner band TB is formed by using the toner of cyan (C) at the time of the next one color print. Is set as follows.

FIG. 6B shows an example of the operation when 2-up printing is performed using the above-described recording paper such as a postcard. In the above-described two-up print example (FIG. 6), the toner band T
In contrast, in this operation example, when performing two color prints, the toner band TB is formed using one of the four color toners (yellow toner in the illustrated example). Is formed, and when the next two color prints are performed, the toner bands TB are formed by using toners of different colors (magenta toner in the illustrated example). Are set to be used sequentially.

When the toner band TB is formed by selectively using four color toners as illustrated in FIGS. 7A and 7B, the plurality of toners are consumed at substantially the same ratio. As a result, it is prevented that only a part of the toner is consumed and lost.

[Other Embodiments] In the first embodiment, an example has been described in which the “paper type of recording paper P”, which is a determination condition for forming a toner band, is initially set with contents for all types. For example, "paper types other than plain paper (thick paper,
(Or OHP sheet, label paper, etc.). " Also, the determination condition may be set to “contents for a case where the secondary transfer bias is set high” instead of “paper type”. These should be set from the viewpoint that the toner band is formed only in a situation where it is necessary to reliably prevent the troubles related to the cleaning blade, and that the other portions are not formed as much as possible (including suppressing waste of toner). Can be.

As the position where the toner band is formed, the specific area G of the intermediate transfer belt 20 (outside the side of the narrow recording paper) G is set to the minimum necessary area as shown in FIG. If necessary, the area on the upstream side in the belt rotation direction from the rear end of the recording sheet (particularly, only the area MH that does not intersect with the area G in FIG. 1: the area with only the lower right diagonal line) is included. The area may be included. When the center registration method is used as the transporting method of the recording paper P, the specific area G exists on both sides of the paper, but the toner band is formed along with the specific area on both sides. Is preferred. Further, when thick paper or an OHP sheet is used as the recording paper P, the fixing device 40 is used more than the case of plain paper in order to secure the fixing property.
In some cases, the feed speed (passing speed) may be reduced. In such a case, it is preferable to form the toner band similarly. Also, if necessary, the toner band
It may be formed at a specific time other than the time of printing.

Further, an image forming apparatus of a type in which a color image is formed by repeating an image forming process four times (cycles) using one image forming unit 10 has been exemplified. A so-called tandem type image forming apparatus may be used in which each image forming unit 10 separately forms a toner image of each color constituting a color image and sequentially primary-transfers it to the intermediate transfer belt 20.

[0069]

As described above, according to the image forming apparatus of the present invention, it is possible to perform image formation (especially, secondary transfer) in a state where the area where the recording medium does not exist in the intermediate transfer body is increased. Even so, the toner image is formed in a specific area of the intermediate transfer body, so that the toner of the toner image is supplied to the cleaning blade, and the toner is applied to the area of the intermediate transfer body where the recording medium does not exist. It is possible to appropriately prevent the occurrence of troubles such as the contact edge portion of the cleaning blade in contact with being turned up or damaged.

Therefore, when such an image forming apparatus is used, it is possible to stably form a good color image without lowering the image quality due to poor cleaning of the intermediate transfer member. . Further, since the formation of the toner image in the specific area is performed simultaneously with the image formation, the productivity does not decrease.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a state of a control operation regarding a toner band.

FIG. 2 is a schematic diagram illustrating the color printer according to the first embodiment.

FIG. 3 is an explanatory diagram showing a relationship (two examples) between an intermediate transfer belt and recording paper (dimensions and feeding directions).

FIG. 4 is a block diagram illustrating a configuration of a control device related to a toner band forming operation.

FIG. 5 is a flowchart illustrating a control operation example regarding a toner band.

FIG. 6 is an explanatory diagram showing a state of a control operation regarding a toner band at the time of 2-up printing.

FIG. 7 is an explanatory diagram showing a state (representative example) of a control operation relating to a toner band during color printing.

8A is a conceptual diagram illustrating an example of a conventional intermediate transfer type image forming apparatus, and FIG. 8B is a partial cross-sectional view illustrating a state in a secondary transfer unit when a narrow recording sheet is used.

FIG. 9 is an explanatory diagram showing a state of a turning phenomenon of a contact edge portion of a cleaning blade.

[Explanation of symbols]

Reference Signs List 10 image forming unit, 11 photosensitive drum, 20 intermediate transfer belt, 25 primary transfer device, 28 cleaning blade, 29 cleaner for belt, 30 secondary transfer device, T toner image, P recording Paper, S ... supply direction, Ws
... width in the supply direction, Ls ... length in the supply direction, TB ... toner band (band-like toner image), M ... transferable area, G ... specific area.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 21/14 G03G 21/00 372 F term (Reference) 2H027 DA23 DA50 DC02 DC04 DC10 DD05 EB06 ED24 ED28 EE02 EE07 EF10 2H030 AD03 BB42 BB54 BB56 2H032 AA05 AA15 BA03 BA05 BA07 BA13 BA19 BA23 BA26 BA30 CA01 CA04 CA13 CA15 2H034 BF01 BF08 BF12

Claims (9)

[Claims] An image forming apparatus for forming a toner image in accordance with image information on an image carrier, and an image forming apparatus which is circulated so as to pass through a transfer portion of the image carrier of the image forming apparatus, is formed on the image carrier. An intermediate transfer member onto which the transferred toner image is transferred, a primary transfer device that primarily transfers the toner image from the image carrier to the intermediate transfer member, and a toner image primarily transferred onto the intermediate transfer member. A secondary transfer device for performing secondary transfer by a transfer electric field formed by applying a secondary transfer bias to a recording medium supplied so as to pass through a transfer unit, and a transfer in which a toner image of the intermediate transfer body is transferred An image forming apparatus comprising: a cleaning device that cleans a surface with a cleaning blade that abuts the transfer surface; and a recognition unit that recognizes a width of the recording medium in a supply direction or a width and a length of the recording medium. When the width in the feeding direction is smaller than a predetermined determination reference width, at least an area of the transferable area of the intermediate transfer body that does not face the recording medium and is outside the side end in the feeding direction of the recording medium. An image forming apparatus, comprising: a control unit that executes control for forming a toner image in a specific area. 2. The image forming apparatus according to claim 1, wherein when the secondary transfer device is configured to variably set a voltage of a secondary transfer bias, the control unit controls the secondary transfer bias. An image forming apparatus configured to execute a control for forming a toner image in the specific area when the voltage is set higher than a predetermined determination reference voltage. 3. The image forming apparatus according to claim 1, wherein the secondary transfer device is configured to variably set a voltage of a secondary transfer bias according to a type of the recording medium, and the recognition is performed. When the means is configured to recognize the type of the recording medium, the control means performs control for forming a toner image in the specific area when the recording medium is a thick paper, an OHP sheet, or a label paper. An image forming apparatus characterized by executing. 4. The image forming apparatus according to claim 1, wherein when the length of the recording medium in a supply direction is shorter than a predetermined determination reference length, the control unit causes the toner image in the specific area to be removed. An image forming apparatus for performing control to be formed in a specific area of an intermediate transfer member, which is located in a region from a rear end of the recording medium in a supply direction to an upstream side in a circumferential movement direction of the intermediate transfer member. 5. The image forming apparatus according to claim 1, wherein the secondary transfer device applies a secondary transfer bias only while the secondary transfer is being performed, and does not apply the bias at other times. In the case, the control unit executes control to form a toner image in the specific area in a specific area of the intermediate transfer body, in which the secondary transfer bias is not applied. Image forming apparatus. 6. The image forming apparatus according to claim 1, wherein the secondary transfer device includes a pressing member that presses and separates the recording medium against the intermediate transfer member during the secondary transfer, and the pressing member performs the secondary transfer. Is configured to be in contact with the intermediate transfer member only while the operation is performed, and otherwise separated from the intermediate transfer member. An image forming apparatus that performs control to be formed in a specific area of the image forming apparatus and an area where the pressing body is separated. 7. The image forming apparatus according to claim 1, wherein the image forming device uses a plurality of toners having different colors to form a plurality of toner images corresponding to the number of colors. In this case, the control unit executes a control for forming a toner image in the specific area by sequentially using the toners of the plurality of colors. 8. The cleaning blade of the cleaning device according to claim 1, wherein the cleaning device is configured to move the cleaning blade toward and away from the intermediate transfer member. An image forming apparatus which executes control for causing the toner image to come into contact with the intermediate transfer member at least when a toner image in the specific area arrives. 9. The image forming apparatus according to claim 1, wherein the control unit executes control for forming a belt-shaped toner image that crosses the specific area as the toner image in the specific area. An image forming apparatus comprising: